Amongst other reasons, the FCC's proposed redistribution of the 27.5 to 29.5 GHz frequency band for Local Multipoint Distribution Services (LMDS) has generated a need for improved antennas. Desired improvements include the ability to more accurately control the pattern of an emitted beam and to facilitate highly power efficient transmission. With respect to LMDS systems, desired improvements also include those which enhance support of broadband two way video communication in a cell-based system.
Prior art attempts, including slotted waveguide antennas, have heretofore been unable to or have had difficulty in developing a millimeter waveguide antenna that is capable of achieving the above objectives in a manner which is both economical and energy efficient. Although relatively efficient millimeter wave antenna architectures have been described, the complexity of many such architectures has resulted in comparatively high production and development costs. For example, the slots of slotted waveguide antennas must be machined to very precise tolerances, thus requiring expensive precision machining and being subject to an undesirably high rejection rate.
With respect to less expensive antennas such as inexpensive planar array antennas and the like (e.g., microstrip printed patch arrays), these devices may provide the requisite directivity, but are typically inefficient due to the utilization of lossy feed networks in the distribution of power to the array radiators.